Integrated paper comprising fibrillated fibers and active agents immobilized therein

ABSTRACT

Disclosed is an integrated paper wherein the paper has capabilities and functionalities provided by both the fiber and the active agent ingredients, and a method of immobilizing the active agents within the integrated paper. The tight pore structure of the integrated paper of the present invention, a mean pore diameter of less than about 2 microns, provides short diffusion distances from a fluid to the surface of the paper ingredients by adsorption or diffusive interception making it an excellent medium for fluid filtration. The integrated paper of the present invention can further include a microbiological interception enhancing agent. The integrated paper can be formed using, preferably, wet laid paper-making processes for speed and efficiency. Also disclosed are devices utilizing the integrated paper useful in fluid filtration.

This is a divisional application of U.S. patent application Ser. No.10/666,878, now U.S. Pat. No. 7,655,112, filed on Sep. 19, 2003, whichis a continuation-in-part of U.S. patent application Ser. No.10/622,882, now U.S. Pat. No. 7,296,691, filed on Jul. 18, 2003 and ofU.S. patent application Ser. No. 10/286,695, now U.S. Pat. No.6,835,311, filed on Nov. 1, 2002, which claims priority from U.S.Provisional Application Ser. No. 60/354,062 filed on Jan. 31, 2002.

The present invention is directed to an integrated paper made withnanofibers, the integrated paper having particles of active agentsimmobilized therein, filtration systems including same, and methods ofmaking and using.

SUMMARY OF THE INVENTION

The present invention is directed to, in a first aspect, an integratedpaper having active particles immobilized therein, the integrated papercomprising of: a plurality of fibers fibrillated at a temperaturegreater than about 30° C., wherein the fibrillated fibers have anaverage fiber diameter of less than about 1000 nm; and active agentscomprising metals, metal salts, metal oxides, alumina, carbon, activatedcarbon, silicates, ceramics, zeolites, diatomaceous earth, activatedbauxite, fuller's earth, calcium sulfate, titanium dioxide, magnesia,magnesium hydroxide, magnesium oxide, manganese oxides, iron oxides,perlite, talc, clay, bone char, calcium hydroxide, calcium salts, orcombinations thereof, wherein the integrated paper has a mean pore sizeof less than or equal to about 2 μm.

The active agents can have different settling velocities such that theintegrated paper has an asymmetric structure when formed by wet-laidprocesses.

Preferably, the integrated paper may further include a microbiologicalinterception enhancing agent.

In another aspect, the present invention is directed to an integratedpaper comprising of: a plurality of fibers fibrillated at a temperaturegreater than about 30° C., wherein the fibrillated fibers have anaverage fiber diameter of less than about 400 nm; and silver oxideparticles admixed with the fibrillated fibers. Preferably, thefibrillated fibers comprise a liquid crystal polymer.

In yet another aspect, the present invention is directed to anintegrated paper comprising of: a plurality of fibers fibrillated at atemperature greater than about 30° C., wherein the fibers have anaverage fiber diameter of less than about 400 nm; and one or more acidneutralizing agents admixed with the fibrillated fibers; wherein theintegrated paper can withstand a hot and corrosive environment of a lubeoil filter. The integrated paper may further include binder fiberparticles. Preferably, the one or more acid neutralizing agentscomprises magnesium oxide, magnesium hydroxide, calcium sulfonate,magnesium sulfonate, calcium phenate, magnesium phenate, or combinationsthereof.

In still yet another aspect, the present invention is directed to anintegrated paper comprising of: a plurality of lyocell fibersfibrillated at a temperature greater than about 30° C., wherein thefibrillated lyocell fibers have an average fiber diameter of less thanor equal to about 400 nm; and activated carbon particles admixed withthe fibrillated lyocell fibers, wherein the integrated paper has a meanflow path of less than about 2 μm. The integrated paper may furtherinclude a microbiological interception enhancing agent, heavy metalreducing agents such as, for example, zeolite or silicate particles,and/or an arsenic reducing agent such as, for example, particles of anoxide of manganese or iron.

In a further aspect, the present invention is directed to an integratedpaper comprising of: a plurality of fibers having an average fiberdiameter of less than about 1000 nm; and a lead reducing agent admixedwith the plurality of fibers, wherein the integrated paper has a meanflow path of less than about 2 μm. The integrated paper may furtherinclude binder fiber particles. The integrated paper may be wrappedaround a carbon block.

In still a further aspect, the present invention is directed to a waterfiltration device comprising of: a carbon block; and an integrated paperupstream of the carbon block, the integrated paper having a mean flowpath of less than about 2 μm and comprising an admixture of: fibrillatedfibers having an average fiber diameter of less than about 1000 nm; andactive agents comprising metals, metal salts, metal oxides, alumina,carbon, activated carbon, silicates, ceramics, zeolites, diatomaceousearth, activated bauxite, fuller's earth, calcium sulfate, titaniumdioxide, magnesia, magnesium hydroxide, magnesium oxide, manganeseoxides, iron oxides, perlite, talc, clay, bone char, calcium hydroxide,calcium salts, or combinations thereof. Preferably, the integrated paperprovides toxic material, heavy metal reduction, and/or a water softeningeffect. The integrated paper may further include a microbiologicalinterception enhancing agent.

In still yet a further aspect, the present invention is directed to agravity-flow water filtration device comprising of: a hydrophilicintegrated paper having a mean flow path of less than about 2 μmcomprising of: fibrillated fibers having an average fiber diameter ofless than about 400 nm; and particles of activated carbon, heavy metalreducing agents, arsenic reducing agents, chemisorbent agents, orcombinations thereof, wherein the gravity-flow water filtration devicehas a flow rate of about 10 to about 1000 ml/minute when operated at apressure of about 4 inches water column. Preferably, the fibrillatedfibers are fibrillated at a temperature of greater than about 30° C.,and may comprise lyocell. Preferably, the average fiber diameter of thefibrillated fibers is smaller than an average particle size of theactivated carbon, heavy metal reducing agents, and chemisorbent agents.The integrated paper may further include a microbiological interceptionenhancing agent.

In still yet a further aspect, the present invention is directed to alube oil filtration device comprising of: an integrated paper in contactwith the lube oil, the integrated paper comprising an admixture of:fibrillated fibers having an average fiber diameter of less than about1000 nm; and an acid neutralizing agent. Preferably, the acidneutralizing agent comprises magnesium hydroxide or magnesium oxide.

In still yet a further aspect, the present invention is directed to anair treatment device for chemisorbing carbon dioxide, the devicecomprising of: an integrated paper comprising an admixture offibrillated fibers having an average fiber diameter of less than about1000 nm; and silver oxide, wherein the fiber diameter of the fibrillatedfibers is smaller than an average particle size of the silver oxide.

In still yet a further aspect, the present invention is directed tomethod of immobilizing particles comprising of: providing a plurality ofactive agents comprising metals, metal salts, metal oxides, alumina,carbon, activated carbon, silicates, ceramics, zeolites, diatomaceousearth, activated bauxite, fuller's earth, calcium sulfate, titaniumdioxide, magnesia, magnesium hydroxide, magnesium oxide, manganeseoxides, iron oxides, perlite, talc, clay, bone char, calcium hydroxide,calcium salts, or combinations thereof; providing a plurality of fiberswherein at least a portion of the fibers have an average fiber diameterthat is smaller than an average particle size of the active particles;admixing the active agents and the fibers; and forming an integratedpaper having a mean flow path of less than about 2 μm with the admixtureof active agents and fibers. Preferably, in the step of providing aplurality of fibers, the plurality of fibers are produced byfibrillation at temperatures of greater than about 30° C. Preferably, inthe step of forming the paper, the paper is loaded with active particlesup to about 95% by weight of the integrated paper.

DETAILED DESCRIPTION OF THE INVENTION

An integrated paper (meaning a paper with capabilities provided by boththe fiber and particulate ingredients) of the present invention has amean pore size of less than about 2.0 microns, preferably less thanabout 1 micron, that includes fibrillated nanofibers having a CanadianStandard Freeness of less than about 100, and an average fiber diameterof less than or equal to about 1000 nm, and active particles immobilizedwithin the integrated paper. The tight pore structure of the integratedpaper of the present invention provides short diffusion distances fromaffluid to the surface of the paper ingredients by adsorption ordiffusive interception making it an excellent medium for fluidfiltration. The integrated paper can be formed using, preferably, wetlaid paper-making processes for speed and efficiency.

The active particles immobilized within the integrated paper cancomprise metals, metal salts, metal oxides, alumina, carbon, activatedcarbon, silicates, ceramics, zeolites, diatomaceous earth, activatedbauxite, fuller's earth, calcium sulfate, titanium dioxide, magnesia,magnesium hydroxide, magnesium oxide, manganese oxides, iron oxides,perlite, talc, clay, bone char, calcium hydroxide, calcium salts, orcombinations thereof. The active particles provide a functionality tothe integrated paper for applications such as, for example, adsorptionof carbon dioxide with silver oxide in air filtration; controllingacidity in lube oil with magnesium oxide/hydroxide; combinations ofactivated carbon and a lead reducing agent, such as zeolites oramorphous titanium silicate as examples, to provide an inexpensivecyst-reducing water filtration medium that also intercepts lead,chlorine, taste, and odors; and immobilizing titanium dioxide for theproduction of photocatalytic membranes.

Furthermore, the fibrillated fibers, or nanofibers, alone or incombination with other ingredients of the integrated paper can betreated with a microbiological interception enhancing agent to impartanti-microbial activity to the integrated paper. Preferably, themicrobiological interception enhancing agent utilizes a synergisticinteraction between a cationic material and a biologically active metal,that when combined, provide broad-spectrum reduction of microbiologicalcontaminants on contact. The charge provided by the cationic material tothe integrated paper aids in electro-kinetic interception ofmicrobiological contaminants, while the tight pore structure provides ashort diffusion path and, therefore, rapid diffusion kinetics ofcontaminants in a flowing fluid to the surface of a surface of thepaper. Due to the dominant role of diffusion for the interception ofextremely small particles, there is a direct correlation between thereduction of contaminants, and the contact time of an influent withinthe integrated paper, rather than a simple dependence upon the thicknessof the paper.

The Fibers

Fibers useful in making the integrated paper of the present inventionare any fibers that can be fibrillated into nanofibers. The fiberspreferably comprise organic polymeric fibers that are capable of beingfibrillated. Fibrillated fibers are most preferred due to theirexceptionally fine dimensions and potentially low cost. Such fibrillatedfibers include, but are not limited to, polymers such as polyamide,acrylic, acrylonitrile, liquid crystal polymers such as VECTRAN®, andthe like; ion-exchange resins; engineered resins; cellulose; rayon;ramie; wool; silk; glass; other fibrous materials; or combinationsthereof. Combinations of organic and inorganic fibers and/or whiskerswhether fibrillated or not, are contemplated and within the scope of theinvention. For example, glass, ceramic, or metal fibers and polymericfibers may be used together. Glass or metal fibers can provideadditional wet strength to the integrated paper. In a most preferredembodiment, fibrillated lyocell fibers are used due to theirexceptionally fine dimensions and potentially low cost.

Fibrillatable cellulose fibers can be made by direct dissolution andspinning of wood pulp in an organic solvent, such as an amine oxide, andare known as lyocell fibers. Lyocell fibers have the advantage of beingproduced in a consistent, uniform manner, thus yielding reproducibleresults, which may not be the case for, for example, natural cellulosefibers. Further, the fibrils of lyocell are often curled. The curlsprovide a significant amount of fiber entanglement. As an addedadvantage, the fibrillated lyocell fibers may be produced in largequantities using equipment of modest capital cost. It will be understoodthat fibers other than cellulose may be fibrillated to produce extremelyfine fibrils, such as for example, synthetic fibers, in particular,acrylic or polyacrylonitrile (PAN) fibers, or other cellulosicmaterials.

When produced by a wet laid process from fibers such as cellulose orpolymer fibers, such nanofibers should have a Canadian Standard Freenessof less than or equal to about 100, preferably less than or equal toabout 45, and most preferably less than or equal to about 0. However, itshould be recognized that in some cases, Canadian Standard Freeness isnot an ideal measure of fiber size, as in the case of extremely stifffibers such as those produced from liquid crystal polymers such asVECTRAN®. In these cases, the fiber size should be directly assayedusing microscopy. Preferably, a significant portion of the nanofibersshould have a diameter less than or equal to about 1000 nanometers, morepreferably less than or equal to about 400 nanometers, and nanofibersless than or equal to about 250 nanometers in diameter are mostpreferred. The diameter of the nanofibers is preferably less than anaverage particle size of said active agents for physical entrapment ofthe active agents. It is preferable to chop the original fibers prior tofibrillation to a length of about 1 millimeter to about 8 millimeters,preferably about 2 millimeters to about 6 millimeters, and morepreferably about 3 millimeters to about 4 millimeters, and to sustainthis fiber length during the fibrillation process by avoiding excessivefiber cutting.

Active Agents for Increased Functionality/Reinforcement

One or more active agents either in particulate, fiber, whisker, orpowder form may be admixed with the nanofibers to provide addedfunctionality and/or reinforcement to the integrated paper. Usefulactive agents may include, but are not limited to, metals, metal salts,metal oxides, alumina, carbon, activated carbon, silicates, ceramics,zeolites, diatomaceous earth, activated bauxite, fuller's earth, calciumsulfate, titanium dioxide, magnesia, magnesium hydroxide, manganeseoxides, iron oxidess, perlite, talc, clay, bone char, calcium hydroxide,calcium salts, or combinations thereof. Such active agents can aid inthe adsorption of contaminants such as heavy metals or volatile organiccompounds (VOCs). The active agents can also be chemically treated toimpart microbiological interception capabilities depending upon theparticular application.

Different types of active agents can impart functionality to theintegrated paper. Not intending to be bound by these or any examplesdisclosed herein, some applications where an integrated paper isparticularly low cost and useful include, but are not limited to, anintegrated paper with silver oxide for chemisorbing carbon dioxide inclosed systems. The silver oxide, upon chemisorption of the carbondioxide, forms silver carbonate. Upon exposure to heat, the silvercarbonate reverts back to silver oxide and the integrated paper can besubject to addition chemisorption of carbon dioxide.

Filtration of industrial oils can be accomplished by filtering the oilthrough a filter medium comprising an integrated paper havingimmobilized therein additives that can boost the performance of the oil.For example only, the acidity of lubrication oil can be controlled byfiltering the oil with an integrated paper containing acid neutralizingagents such as, for example, magnesium oxide or magnesium hydroxide.Preferably, in order to withstand the high working temperatures ofindustrial oil, the integrated paper is made with a synthetic fiber suchas a liquid crystal polymer.

Other active agents include activated carbon, alone or in combinationwith a lead reducing agent, such as a titanium zeolite or amorphoussilicate as examples. Such a zeolite-loaded integrated paper can alsocontain activated carbon and can be manufactured with a pore structuresuitable for the direct interception of microbiological threats such asprotozoan cysts, bacteria, or viral particles. Such an integrated papercan provide inexpensive cyst-reducing capabilities with lead, chlorine,taste, and odor reduction. The zeolite integrated paper can provide awater-softening effect by direct ion-exchange. Incorporating iron oxidesor manganese oxides into the integrated paper, alone or in combinationwith other active agents, further provides arsenic reduction capabilitydesirable in a water filtration medium. These papers can be used inconjunction with carbon block filtration media to boost performance ofthe entire filter system for little additional cost.

Integrated papers having immobilizing titanium dioxide therein areuseful in photocatalytic processes, and are inexpensive and easy tomanufacture using paper making processes.

The active agents are preferably present in a sufficient amount suchthat the fluid flow through the integrated paper is not substantiallyimpeded when used as a filter medium. The amount of active agents isalso dependent upon the particular use of the filtration system.Preferably, the active agents are present in an amount of up to about 50weight percent based on a total weight of the integrated paper, and morepreferably up to about 75 weight percent. Higher concentrations ofactive agents, such as up to about 95 weight percent, are contemplatedand within the scope of the invention. The particle size of the activeagents can be about 1 to about 5000 μm. As the size of the active agentsdecrease, higher loading rates of the active agents in the paper can beobtained.

One or more active agents can be chosen wherein particles of the one ormore active agents have different settling velocities during productionof the integrated paper. The resultant paper would have one or moreparticles settling to one surface of the paper and the fibers settlingto the other surface such that an asymmetric pore gradient existsthrough the thickness of the paper. This asymmetry can produce agradient in the pore structure from a prefiltration structure to a finalpolishing filter. For example, activated carbon particles can be admixedwith nanofibers having a different density and settling velocity thanthe activated carbon particles such that under gravity conditions duringinitial paper formation form a gradient with a zone of nanofibersleading into a zone of activated carbon particles. An influentcontacting an integrated paper of this type would be stripped ofchemical impurities when first contacted with the activated carbon andfollowed by removal of particulate impurities when in contact with thenanofibers.

The strength of the integrated paper, especially when wet, may beimproved with the addition of various active agents that can bereinforcing additives or binders. It is well known in the art that theaddition of epoxy or acrylic or other resins to the paper making processcan provide enhanced wet strength, but these water-dispersed resinsoften cause lower permeability to the final product, especially as fibersize becomes very small. Although these resins and resin systems can beused in the current invention, it is preferable to use thermoplastic orthermoset materials known in the art, and in either liquid, powder,particulate or fiber form.

Useful binders include, but are not limited to, polyolefins, polyvinylhalides, polyvinyl esters, polyvinyl ethers, polyvinyl sulfates,polyvinyl phosphates, polyvinyl amines, polyamides, polyimides,polyoxidiazoles, polytriazols, polycarbodiimides, polysulfones,polycarbonates, polyethers, polyarylene oxides, polyesters,polyarylates, phenol-formaldehyde resins, melamine-formaldehyde resins,formaldehyde-ureas, ethyl-vinyl acetate copolymers, co-polymers andblock interpolymers thereof, and combinations thereof. Variations of theabove materials and other useful polymers include the substitution ofgroups such as hydroxyl, halogen, lower alkyl groups, lower alkoxygroups, monocyclic aryl groups, and the like. Other potentiallyapplicable materials include polymers such as polystyrenes andacrylonitrile-styrene copolymers, styrene-butadiene copolymers, andother non-crystalline or amorphous polymers and structures.

A more detailed list of binders that may be useful in the presentinvention include end-capped polyacetals, such as poly(oxymethylene) orpolyformaldehyde, poly(trichloroacetaldehyde), poly(n-valeraldehyde),poly(acetaldehyde), and poly(propionaldehyde); acrylic polymers, such aspolyacrylamide, poly(acrylic acid), poly(methacrylic acid), poly(ethylacrylate), and poly(methyl methacrylate); fluorocarbon polymers, such aspoly(tetrafluoroethylene), perfluorinated ethylene-propylene copolymers,ethylene-tetrafluoroethylene copolymers, poly(chlorotrifluoroethylene),ethylene-chlorotrifluoroethylene copolymers, poly(vinylidene fluoride),and poly(vinyl fluoride); polyamides, such as poly(6-aminocaproic acid)or poly(e-caprolactam), poly(hexamethylene adipamide),poly(hexamethylene sebacamide), and poly(11-aminoundecanoic acid);polyaramides, such as poly(imino-1,3-phenyleneiminoisophthaloyl) orpoly(m-phenylene isophthalamide); parylenes, such as poly-2-xylylene,and poly(chloro-1-xylylene); polyaryl ethers, such aspoly(oxy-2,6-dimethyl-1,4-phenylene) or poly(p-phenylene oxide);polyaryl sulfones, such aspoly(oxy-1,4-phenylenesulfonyl-1,4-phenyleneoxy-1,4-phenyl-eneisopropylidene-1,4-phenylene),andpoly(sulfonyl-1,4-phenylene-oxy-1,4-phenylenesulfonyl4,4′-biphenylene);polycarbonates, such as poly-(bisphenol A) orpoly(carbonyldioxy-1,4-phenyleneisopropylidene-1,4-phenylene);polyesters, such as poly(ethylene terephthalate), poly(tetramethyleneterephthalate), and poly(cyclohexyl-ene-1,4-dimethylene terephthalate)or poly(oxymethylene-1,4-cyclohexylenemethyleneoxyterephthaloyl);polyaryl sulfides, such as poly(p-phenylene sulfide) orpoly(thio-1,4-phenylene); polyimides, such aspoly(pyromellitimido-1,4-phenylene); polyolefins, such as polyethylene,polypropylene, poly(1-butene), poly(2-butene), poly(1-pentene),poly(2-pentene), poly(3-methyl-1-pentene), and poly(4-methyl-1-pentene);vinyl polymers, such as poly(vinyl acetate), poly(vinylidene chloride),and poly(vinyl chloride); diene polymers, such as1,2-poly-1,3-butadiene, 1,4-poly-1,3-butadiene, polyisoprene, andpolychloroprene; polystyrenes; and copolymers of the foregoing, such asacrylonitrilebutadiene-styrene (ABS) copolymers. Polyolefins that may beuseful include polyethylene, linear low density polyethylene,polypropylene, poly(1-butene), poly(2-butene), poly(1-pentene),poly(2-pentene), poly(3-methyl-1-pentene), poly(4-methyl-1-pentene), andthe like.

A range of binder fibers, including polyethylene, polypropylene,acrylic, or polyester-polypropylene or polypropylene-polyethylenebi-component fibers, or others can be used. Certain types of treatedpolyethylene fibers, when properly treated, as described below, areoptimal, and have the additional benefit of not significantlyinterfering with the hydrophilic nature of the resulting filter mediumwhen used in modest volumes. Preferred fiber binder materials mayinclude FYBREL® synthetic fibers and/or SHORT STUFF® EST-8, both ofwhich are polyolefin based. FYBREL® is a polyolefin based synthetic pulpthat is a highly fibrillated fiber and is commercially available fromMitsui Chemical Company, Japan. FYBREL® has excellent thermalmoldability and provides a smooth surface to the filter medium. SHORTSTUFF® EST-8 is commercially available from MiniFibers, Inc.,Pittsburgh, Pa., and is a highly fibrillated, high density polyethylene.

Preferably, one or more binders are present in an amount of about 1% toabout 10% by weight, more preferably about 3% to about 6%, and mostpreferably about 5%. It is preferable that the binder material have asoftening point that is significantly lower than a softening point ofthe nanofiber material so that the filter medium can be heated toactivate the binder material, while the integrated paper does not meltand thereby lose porosity.

As the size of the active agents decrease, high loading rates of theactive agents in the paper can be obtained. Preferably, the diameter ofthe binder fibers is equal to or less than the particle size of theactive agents to effectively immobilize the active agents within thepaper. Alternatively, in a binder-less paper, the diameter of thenanofibers is preferably equal to or less than the particle size of theactive agents to effectively immobilize the active agents in the paperby physical entrapment. The smaller the particles of active agents are,the greater the diffusion kinetics for more effective interception ofcontaminants that are smaller than the mean flow path diameter.

The Integrated Paper as an Anti-Microbial Filter Medium

The tight pore structure of the integrated paper provides a shortdiffusion path and, therefore, rapid diffusion kinetics ofmicrobiological contaminants in a flowing fluid to the surface of theintegrated paper. The tight pore structure also provides supplementaldirect mechanical interception of microbiological contaminants. The meanpore size of the integrated paper is less than about 2 microns,preferably less than about 1 micron, and can be less than about 0.5microns. Thus, it would be advantageous to treat the fibers and/oractive agents to impart anti-microbial properties to the integratedpaper to further enhance microbiological contaminant removal.

The nanofibers and/or active agents, or the integrated paper itself, canbe chemically treated with any compatible microbiological interceptionenhancing agent known in the art, with or without a biologically activemetal. Examples of suitable anti-microbial agents include, withoutlimitation, any bactericidal agent, bacteriostatic agent, fungicidalagent, fungistatic agent, or the like, that are preferably efficaciousagainst a broad spectrum of microbes. Specific examples of suitablebactericidal/bacteriostatic agents include, without limitation,POLYMYCIN™, BACITRACIN™, lysozyme, TRICLOSAN™, DOWCIDE™, quaternaryamine salts, polyphenols, acid-anionic surfactants, amphotericsurfactant disinfectants, biguanidines, and the like. Specific examplesof suitable fungicidal/fungistatic agents include, without limitation,dithiocarbamates, phthalimides, dicarboximides, organophosphates,benzimidazoles, carboxanilides, phenylamides, phosphites, and the like.

Preferably, the microbiological interception enhancing agent is capableof creating a positive charge on the surface of the nanofibers toenhance the electro-kinetic interception of microbiologicalcontaminants. The chemical treatment produces a strong positive chargeupon the treated surfaces as measured using streaming or zeta potentialanalysis and this positive charge is retained at pH values below 10. Thecationic material may be a colloid, a small charged molecule or a linearor branched polymer having positively charged atoms along the length ofthe polymer chain. The cationic material has a counter ion associatedtherewith. Preferably, the cationic material is water soluble andreadily ionizes in an aqueous medium, but has the capacity to be bonded,adsorbed, or incorporated into the surface or bulk of the nanofibers oractive agents. The cationic material is present on at least a portion ofthe surface of the nanofibers or active agents. The microbiologicalinterception enhancing agent further includes a biologically activemetal in direct proximity to the cationic material.

If the cationic material is a polymer, the charge density is preferablygreater than about 1 charged atom per about every 30 Angstroms,preferably greater than about 1 charged atom per about every 20Angstroms, and more preferably greater than about 1 charged atom perabout every 10 Angstroms of molecular length. The higher the chargedensity on the cationic material, the higher the concentration of thecounter ion associated therewith. A high concentration of an appropriatecounter ion can be used to drive the precipitation of the biologicallyactive metal. The high charge density of the cationic material providesthe ability to adsorb and significantly reverse the normal negativecharge of the nanofibers making it more useful as a microbiologicalinterception enhanced filter medium. The cationic material shouldconsistently provide a highly positively charged surface to thenanofibers as determined by a streaming or zeta potential analyzer,whether in a high or low pH environment.

The use of a cationic polymer of sufficiently high molecular weightallows treatment of the surfaces of the nanofibers without seriousattendant impact upon any adsorptive capabilities of the mezo-pores andmicro-pores of the carbon or activated carbon immobilized within theintegrated paper. The cationic material can have a molecular weightgreater than or equal to about 5000 Daltons, preferably greater than orequal to 100,000 Dalton, more preferably greater than or equal to about400,000 Daltons, and can be greater than or equal to about 5,000,000Daltons.

The cationic material includes, but is not limited to, quaternizedamines, quaternized amides, quaternary ammonium salts, quaternizedimides, benzalkonium compounds, biguanides, cationic aminosiliconcompounds, cationic cellulose derivatives, cationic starches,quaternized polyglycol amine condensates, quaternized collagenpolypeptides, cationic chitin derivatives, cationic guar gum, colloidssuch as cationic melamine-formaldehyde acid colloids, inorganic treatedsilica colloids, polyamide-epichlorohydrin resin, cationic acrylamides,polymers and copolymers thereof, combinations thereof, and the like.Charged molecules useful for this application can be small moleculeswith a single charged unit and capable of being attached to at least aportion of the nanofibers. The cationic material preferably has one ormore counter ions associated therewith which, when exposed to abiologically active metal salt solution in an aqueous medium, causepreferential precipitation of a colloidal metal precipitate in directproximity to the cationic material. The counter ion associated with thecationic material preferentially precipitates with at least a portion ofthe cation of the biologically active metal salt such that controlledand direct precipitation of a colloidal metal precipitate occurs inproximity to the cationic material. The colloidal metal precipitate, aspecies comprising of the metal cation and counter ion of the cationicmaterial, is physically trapped within a matrix of the cationicmaterial, or bound to the cationic material either by adsorption, orelectrostatic forces.

Exemplary of amines may be pyrroles, epichlorohydrin derived amines,polymers thereof, and the like. Exemplary of amides may be thosepolyamides disclosed in International Patent Application No. WO01/07090, and the like. Exemplary of quaternary ammonium salts may behomopolymers of diallyl dimethyl ammonium halide, epichlorohydrinderived polyquaternary amine polymers, quaternary ammonium salts derivedfrom diamines and dihalides such as those disclosed in U.S. Pat. Nos.2,261,002, 2,271,378, 2,388,614, and 2,454,547, all of which areincorporated by reference, and in International Patent Application No.WO 97/23594, also incorporated by reference,polyhexamethylenedimethylammonium bromide, and the like. The cationicmaterial may be chemically bonded, adsorbed, or crosslinked to thenanofiber and/or to an active particle or fiber captured within thenanofiber material.

Furthermore, other materials suitable for use as the cationic materialinclude BIOSHIELD® available from BioShield Technologies, Inc.,Norcross, Ga. BIOSHIELD® is an organosilane product includingapproximately 5% by weight octadecylaminodimethyltrimethoxysilylpropylammonium chloride and less than 3% chloropropyltrimethoxysilane. Anothermaterial that may be used is SURFACINE®, available from SurfacineDevelopment Company LLC, Tyngsboro, Mass. SURFACINE® comprises athree-dimensional polymeric network obtained by reactingpoly(hexamethylenebiguanide) (PHMB) with4,4′-methlyene-bis-N,N-dilycidylaniline (MBGDA), and a crosslinkingagent, to covalently bond the PHMB to a polymeric surface. Silver, inthe form of silver iodide, is introduced into the network, and istrapped as submicron-sized particles. The combination is an effectivebiocide, which may be used in the present invention.

The cationic material when exposed to an aqueous biologically activemetal salt solution forms the colloidal metal precipitate thatprecipitates onto at least a portion of the surface of at least some ofthe nanofibers and/or active agents. For this purpose, the metals thatare biologically active are preferred. Such biologically active metalsinclude, but are not limited to, silver, copper, zinc, cadmium, mercury,antimony, gold, aluminum, platinum, palladium, and combinations thereof.The most preferred biologically active metals are silver and copper. Thebiologically active metal salt solution is preferably selected such thatthe metal and the counter ion of the cationic material are substantiallyinsoluble in an aqueous environment to drive precipitation of thecolloidal metal precipitate. Preferably, the metal is present in anamount of about 0.01% to about 2.0% by weight of the nanofibers.

A particularly useful microbiological interception enhancing agent is asilver-amine-halide complex. The cationic amine is preferably ahomopolymer of diallyl dimethyl ammonium halide having a molecularweight of about 400,000 Daltons or other quaternary ammonium saltshaving a similar charge density and molecular weight. A homopolymer ofdiallyl dimethyl ammonium chloride useful in the present invention iscommercially available from Nalco Chemical Company of Naperville, Ill.,under the tradename MERQUAT® 100. The chloride counter ion may bereplaced with a bromide or iodide counter ion. When contacted with asilver nitrate solution, the silver-amine-halide complex precipitates onat least a portion of the nanofibers. Such microbiological interceptionenhancing agents are taught in co-pending U.S. patent application Ser.No. 10/286,695 filed on Nov. 1, 2002, hereby incorporated by referencein its entirety.

Methods of Making the Integrated Paper of the Present Invention

The integrated paper of the present invention may be made using wet ordry laid processes, as well as other processes known to one of skill inthe art. Dry laid processes include spun bonding, electrospinning,spinning islands-in-sea processes, fibrillated films, melt blowing, andother dry laid processes known to one of skill in the art. An exemplarydry laid process starts with staple fibers, which can be separated bycarding into individual fibers and are then laid together to a desiredthickness by an aerodynamic or hydrodynamic process to form an unbondedfiber sheet. The unbonded fibers can then be subjected to hydraulic jetsto both fibrillate and hydroentangle the fibers. Active agents can beincorporated into the precursor paper by dropping the active agents ontothe fiber sheet as the nanofibers are laid. A similar process can beperformed on certain plastic films that when exposed to high pressurejets of water, are converted into webs of fibrillated fibers. Activeagents can be incorporated into the precursor paper by dropping theactive agents onto the fiber sheet as the nanofibers are laid.

In a preferred wet laid process, a fiber tow is chopped to a specificlength, usually in the range of about 1 millimeter to about 8millimeters and in particular in the range of about 3 millimeters toabout 4 millimeters. The chopped fibers are fibrillated in a devicehaving characteristics similar to a blender, or on a large scale, inmachines commonly referred to as a “hi-low”, a “beater” or a “refiner”.The fiber is subjected to repetitive stresses, while further choppingand the reduction of fiber length is minimized. As the fibers undergothese stresses, the fibers split as a result of weaknesses betweenamorphous and crystalline regions and the Canadian Standard Freeness(CSF), which is determined by a method well known in the art, begins todecline. Samples of the resulting pulp can be removed at intervals, andthe CSF used as an indirect measure of the extent of fibrillation. Whilethe CSF value is slightly responsive to fiber length, it is stronglyresponsive to the degree of fiber fibrillation. Thus, the CSF, which isa measure of how easily water may be removed from the pulp, is asuitable means of monitoring the degree of fiber fibrillation wheneverthe fibers have a good tendency to form a wet-laid sheet. However, thisis not necessarily the case when handling very stiff fibers such asthose made from liquid crystal polymers such as VECTRAN®. If the surfacearea is very high, then very little water will be drained from the pulpin a given amount of time and the CSF value will become progressivelylower as the fibers fibrillate more extensively. Preferably,fibrillation occurs at temperatures greater than about 30° C. toaccelerate the process. Enzymes may be added to further accelerate thefibrillation process.

The fibrillated fibers of a given CSF value can be directly used forproducing paper or dewatered on a variety of different devices,including a dewatering press or belt, to produce a dewatered pulp. Thedewatered pulp can be subsequently used to make a wet-laid paper.Generally, for application in the present invention, a pulp with a CSFof below 100 is used, preferably, the CSF should be less than or equalto about 45, and more preferably less than or equal to about 0. ACanadian Standard Freeness below 0 is achieved when the fibers arefibrillated beyond the time needed to achieve a Canadian StandardFreeness of 0. The fibers can be directly sent to pulp preparationsystems to create a furnish suitable for paper making. Functional activeagents are slurried with the fibrillated fibers prior to being sent to apaper making machine. To impart anti-microbial properties to theintegrated paper, the fibrillated fibers alone or in combination withthe active and/or reinforcing agents can be treated with amicrobiological interception enhancing agent.

In one preferred embodiment, the nanofibers and/or active agents can betreated with a cationic material in such a manner as to allow thecationic material to coat at least a portion of the surface of at leastsome of the nanofibers and/or active agents thereby imparting a chargeon the nanofibers and/or active agents. Methods of applying the cationicmaterial to the nanofibers and/or active agents are known in the art andinclude, but are not limited to, spray, dip, or submergence coating tocause adsorption, chemical reaction or crosslinking of the cationicmaterial to the surface of the nanofibers and/or active agents. Thetreated pulp is then rinsed in reverse osmosis/deionized (RO/DI) water,partially dewatered, usually under vacuum, to produce a wet lap that canthen be exposed to a biologically active metal salt solution. The use ofnearly ion-free rinse water causes the counter-ions associated with thecationic material to be drawn tightly against the treated surface and toeliminate unwanted ions that may cause uncontrolled precipitation of thebiologically active metal into sites remote from the cationic surface.

A metal salt solution is infiltrated into the nanofibers and/or activeagents to allow precipitation of the colloidal metal precipitate on asurface of at least a portion of the nanofibers and/or active agents.The precipitation accurately deposits a colloidal metal precipitateadjacent to the cationic coating because the counter-ion associated withthis coating reacts with the applied metal salt to form the colloidalparticles. After sufficient exposure to the biologically active metalsalt solution, the nanofibers can be rinsed and excess water is removed.When silver nitrate is used as the metal salt solution, the presence ofprecipitated silver can be confirmed by using a Kratos EDX-700/800 X-rayfluorescence spectrometer available from Kratos Analytical, a ShimadzuGroup Company, Japan.

Alternatively, once the nanofibers are treated with the microbiologicalinterception enhancing agent, they can be admixed with untreated activeand/or reinforcing agents. The fiber mixture can be directly sent topulp preparation systems to create a furnish suitable for paper making.

Exemplary of a wet laid process includes mixing a pulp of fibrillatedlyocell fibers having a Canadian Standard Freeness of about 0 with 5%EST-8 binder fibers, and the active agents to form a slurry in deionizedwater. A furnish is formed with about 1% to about 2% consistency. It ispreferable to add the microbiological interception enhancing agent tothe slurry, if anti-microbial properties are desired in the finalintegrated paper. Next, this pulp is partially dewatered under vacuumand rinsed with deionized water to form a wet lap. Thereafter, the fiberslurry can be directly used in the production of the integrated paper.It is preferable to send the slurry directly into a paper making machinewhere the economies of scale are easily achieved in making aninexpensive integrated paper for use as a filter medium.

The sheet can also be densified during the paper-making process bypassing the precursor paper through a wet press or through the use of acalendar to achieve maximum density in the final product. Heatedcalendaring of the sheet can produce fiber-fiber and fiber-particlebonds resulting in a densified paper with minimal tendency to shedfibers or particles.

An exemplary dry laid process starts with staple fibers, which can beseparated by carding into individual fibers and are then laid togetherto a desired thickness by an aerodynamic process to form an unbondedfiber sheet. The unbonded fibers can then be subjected to hydraulic jetsto both fibrillate and hydroentangle the fibers. A similar process canbe performed on certain plastic films that when exposed to high pressurejets of water, are converted into webs of fibrillated fibers. Activeagents can be incorporated into the precursor paper by dropping theactive agents onto the fiber sheet as the nanofibers are laid. Again,heated calendaring of the sheet can produce a highly densified paper.

An exemplary paper making process uses a furnish with a consistency ofup to about 1% by weight in the machine chest. The wet lap moves throughthe machine at a rate of about 0.1 to about 15 feet/min (about 0.03 toabout 4.6 m/min). The press section pressure is about 10 to about 60psi. Optionally, the paper may be further calendared under heat andpressure to densify the paper. An integrated paper of the presentinvention having a pore gradient formed from one or more active agentshaving different densities and settling velocities from each otherand/or the nanofibers can be made using paper making processes whereinone or more machine chests are used.

Filtration Devices Utilizing the Integrated Paper

Many types of devices incorporating the integrated paper can beimagined. Described below are certain specific embodiments. However,these devices are exemplary and should not be construed as restrictingthe scope of the invention.

Gravity-Flow Water Filtration Systems

One embodiment of the integrated paper of the present invention usefulin point-of-use gravity-flow water filtration systems includesfibrillated fibers and particles of activated carbon and heavy metalreducing agents. The mean flow path of the activated carbon integratedpaper is less than about 2 pm, and preferably less than about 1 pm. Thetight pore structure easily allows for mechanical interception of thelarger microbiological contaminants such as protozoan cysts. Addition ofthe microbiological interception enhancing agent aids in electro-kineticadsorption of smaller particles such as bacteria and viruses.Preferably, this integrated paper is hydrophilic either by usinghydrophilic fibers or rendered hydrophilic with agents known in the artthat would not foul the pore structure. By adding heavy metal reducingagents such as zeolites, iron oxides, manganese oxide, and the like, theintegrated paper provides an inexpensive filter medium that can providechlorine, taste, odor, lead, and arsenic reduction and microbiologicalinterception. Flow rates can range from about 50 to about 80 ml/minutefor a 3 in² (19.4 cm²) piece of integrated paper. Pleating or foldingthis type of integrated paper increases the surface area for improveddiffusive interception of chemical and microbiological contaminants. Theouter layers of the integrated paper protect the inner layers fromfouling due to exposure to natural organic matter (NOM) such as humicand fulvic acids.

Pressurized Water Filtration Systems

An integrated paper of the present invention can be used in conjunctionwith carbon block filtration media well known in the art. Rather thanincorporating the active agents in the bulk carbon block where therewould be greater axial dispersion due to the dispersion of the activeagents through the structure, the active agents are immobilized in theintegrated paper and wrapped around or within the interior core of thecarbon block. The axial dispersion of the active agents is thencollapsed within the integrated paper where the interstitial spacesbetween the particles of active agents are minimized. Addition of theintegrated paper wrap to any carbon block provides inexpensive chemicaland microbiological reduction capabilities. Water softening agents suchas, for example, zeolites, can be incorporated into the integrated paperfor additional functionality. The integrated paper of the presentinvention can be used in conjunction with a MATRIKX® carbon blockfiltration media sold by KX Technologies LLC, West Haven, Conn.

Lube Oil Filtration Systems

Engine lube oils must have properties that can effectively preventcorrosion and wear, and often contain additives such as highly basicmetallic salts, especially calcium and magnesium salts, as acidneutralizing agents to neutralize the sulfuric acid that is produced asa result of the high sulfur content in certain fuels, especially dieselfuel. A low cost solution would be to incorporate into the lube oilfilter paper the additives needed to maintain performance. An integratedpaper of the present invention incorporating such additives as acidneutralizing agents such as, but not limited to, magnesium oxide,magnesium hydroxide, calcium or magnesium sulfonates, calcium ormagnesium phenates, and the like, can be used alone or in conjunctionwith an activated carbon filter medium to effectively maintain theperformance of the lube oil.

Air Treatment Systems

The integrated paper of the present invention can effectively providechemical and biological protection in air treatment systems. Preferably,the integrated paper has immobilized therein activated carbon, inparticular an impregnated carbon such as, for example, ASZM-TEDA carbon,zeolites, metal impregnated minerals, other specialized materials suchas copper or calcium sulfates or sulphonates, silver oxide, andcombinations thereof. Such air treatment systems can include filtrationmedia incorporating the integrated paper into pleated panels, with orwithout a supporting substrate, for building HVAC systems; respirators;and collective protection applications in shelters, armored fightingvehicles or any other closed space.

EXAMPLES

The following examples are provided to illustrate the present inventionand should not be construed as limiting the scope of the invention.

Hand sheets of the integrated papers in the following examples were madewith fibrillated nanofibers using the following general method.Materials were weighed out and blended with 2.0 L deionized water for atleast 5 minutes in a stainless steel Waring blender. The deionized watermay be heated to temperatures greater than about 30° C. When non-lyocellfibers were used, they were blended separately for about 3 minutes priorto mixing with any fibrillated lyocell nanofibers. Functional active orreinforcing agents were periodically slurried and blended with the fibermixture. The fiber mixture was poured into a 30.5×30.5 cm² stainlesssteel FORMAX™ paper making deckle with a sheet of REEMAY™ 2004 nonwovenlaid over the 100 mesh base screen as a support layer. The deckle wasfilled to a total of about 12 L of water containing the various fibersand functional active or reinforcing agents. A 30.5×30.5 cm² stainlesssteel agitator plate having 60 holes of 2 cm diameter was used to plungethe ingredients up and down from top to bottom about 8 to 10 times. Thewater was removed from the fiber mixture by pulling a slight vacuumbelow the deckle to cause the fibers to form on the REEMAY™ nonwoven.Once the bulk of the water is removed, supplemental dewatering isaccomplished with a vacuum pump to remove additional excess moisture andto create a relatively smooth, flat, fairly thin paper-like sheet. Theresulting sheet is separated from the screen and combined with a blottersheet on both top and bottom. The combination of sheets is gently rolledwith a 2.27 kg marble rolling pin to remove excess water and smooth outthe top surface of the sheet. The sheet is then placed between two freshand dry blotter sheets and placed on a FORMAX® sheet dryer for about 10to about 15 minutes at about 120° C. The REEMAY™ nonwoven sheet isseparated and discarded at this point. Commercial manufacture of theprecursor paper can be accomplished on a Fournier wire, rotoformer, orsimilar systems.

Examples 1 to 4 Integrated Silver Oxide Paper of the Present Invention

Multiple sheets of silver oxide (Ag₂O) paper were made according to theprocedure described above using lyocell nanofibers having a CanadianStandard Freeness of less than about 0 (“CSF-X” fiber). The highlyloaded, integrated silver oxide paper is useful in absorbing carbondioxide for applications such as, but not limited to, respirators andother air treatment apparatus. Proportions of the nanofibers, dryweight, and silver oxide are outlined in Table I. All of these papersallowed the silver oxide to adsorb carbon oxide forming silvercarbonate, and could be regenerated by heating back to silver oxide forfurther adsorption. The nanofibers easily held the roughly 10 micronsilver oxide particles.

TABLE I Ex # 1 2 3 4 Ag₂O 60.0 g 60.0 g 60.0 g 319.2 g CSF-X  6.0 g  3.0g  3.0 g  16.8 g

Examples 5 to 8 Integrated Carbon Paper of the Present Invention

An integrated paper was made according to the procedure described abovewith the addition of carbon and amorphous titanium silicate (ATS) to aidin the adsorption of lead and chlorine with a mean pore size between 0.5to 0.7 microns to promote bacterial filtration. Paper ingredients werefibrillated lyocell fibers having a Canadian Standard Freeness of about0; bituminous coal based carbon ground to a particle size of 85×325 meshwith 28% by weight −325 mesh powder; glass microfibers from JohnsMansville Company, Denver, Colo., under the trade designationFIBREGLASS™ #106; ATS from Engelhard Corporation, Iselin, N.J.; andSHORT STUFF® EST-8 polyethylene fibers commercially available fromMiniFibers, Inc., Pittsburgh, Pa. Proportions in dry weight of theintegrated carbon papers are shown in Table II below. All examplesproduced papers having a mean pore size between 0.5 to 0.7 micronssufficient to filter out bacterial contaminants, as well as protozoancysts.

TABLE II Ex # 5 6 7 8* CSF 0 10.50 g  9.45 g 3.50 g 10.50 g  ATS 7.00 g7.00 g 7.00 g 7.00 g EST-8 3.50 g 2.80 g 2.10 g 2.80 g Glass 1.75 g 3.50g 10.20 g  2.45 g Carbon 12.25 g  12.30 g  12.25 g  12.30 g *Ingredients cast on tea bag paper and later removed.

The paper of Example 8 was further tested for its ability to removelead. A 3.25 inch (8.26 cm) diameter disc of the paper was fitted into ahousing with a head pressure of 5 inches (12.7 cm) and challenged with 3gallons of water having a lead content of 150 ppb lead at a pH of about9. The integrated paper of the present invention as embodied in Example8 was able to reduce the lead concentration to below 10 ppb lead, and insome cases undetectable levels, at flow rates of about 28 to 32ml/minutes.

Example 9 Integrated Magnesium Hydroxide Paper of the Present Invention

An integrated paper was made in accordance with the procedure describedabove with 8.8 g of fibrillated lyocell fibers having a CanadianStandard Freeness of about 23, 91.3 g magnesium hydroxide, 6.6 g ofSHORT STUFF® EST-8 polyethylene fibers, and 3.3 g abaca fibers. Theresultant paper had a basis weight of 104.25 g/ft², a thickness of 1.53millimeters. The mean pore diameter of the integrated magnesiumhydroxide paper is less than about 1 micron. The magnesium hydroxidepaper is suitable for controlling acidity in lube oils.

The integrated paper of the present invention provides an economicalfilter medium useful in removing microbiological and chemicalcontaminants. The paper can be made using paper-making processes forspeed and efficiency. Active particles immobilized therein providefunctionality to the integrated paper for applications such asadsorption of carbon dioxide with silver oxide in air filtration;controlling acidity in lube oil with magnesium hydroxide/oxide;combinations of activated carbon, a lead reduction zeolite, and/or anarsenic to provide an inexpensive cyst-reducing water filtration mediumthat also intercepts lead, chlorine, and odors while improving taste;and immobilizing titanium dioxide for the production of photocatalyticmembranes.

While the present invention has been particularly described, inconjunction with a specific preferred embodiment, it is evident thatmany alternatives, modifications and variations will be apparent tothose skilled in the art in light of the foregoing description. It istherefore contemplated that the appended claims will embrace any suchalternatives, modifications and variations as falling within the truescope and spirit of the present invention.

What is claimed is:
 1. A method of immobilizing particles comprising thefollowing steps in the sequence set forth: providing fibers;fibrillating said fibers at a temperature greater than about 30° C. toform fibrillated fibers having an average fiber diameter of less thanabout 1000 nm; providing a plurality of active agents wherein an averagediameter of said fibrillated fibers is less than an average particlesize of said active agents; treating at least a portion of at least someof said fibrillated fibers and/or said active agents with amicrobiological interception enhancing agent, said microbiologicalinterception enhancing agent comprising a colloidal metal-cationiccomplex of a biologically active metal precipitated with a counter ionof a cationic material residing on said at least portion of said atleast some of said fibrillated fibers and/or said active agents wherebythe colloidal metal precipitates adjacent to the cationic material;admixing together said fibrillated fibers and said active agent;immobilizing said microbiological interception enhancing agent treatedadmixed fibrillated fibers and active agent into an integrated paperhaving a mean flow path of less than about 2 μm whereby said immobilizedfibrillated fibers, active agents and microbiological interceptionenhancing agent reside within and throughout an entire thickness of saidintegrated paper.
 2. The method of claim 1 wherein said microbiologicalinterception enhancing agent is formed only on said fibrillated fibers.3. The method of claim 1 wherein said microbiological interceptionenhancing agent is formed only on said active agents.
 4. The method ofclaim 1 wherein said microbiological interception enhancing agent isformed on both said fibrillated fibers and said active agents.
 5. Themethod of claim 1 wherein said fibrillated fibers or said active agentsare treated with said microbiological interception enhancing agent priorto admixing together.
 6. The method of claim 1 wherein said fibrillatedfibers or said active agents are treated with said microbiologicalinterception enhancing agent subsequent to admixing together.
 7. Themethod of claim 1 further comprising the steps of forming saidmicrobiological interception enhancing agent in the sequence set forthcomprising: coating said at least portion of at least some of saidfibrillated fibers and/or said active agents with said cationicmaterial; rinsing said coated fibrillated fibers and/or said activeagents with a nearly ion-free rinse water; exposing said rinsed, coatedfibrillated fibers and/or said active agents to a biologically activemetal salt solution, such that, said biologically active metalprecipitates with said counter ion of said cationic material to formsaid colloidal metal precipitate adjacent to the cationic material, saidnearly ion-free rinse water enabling said counter ion to be drawntightly against said coated fibrillated fibers and/or said active agentsand eliminating unwanted ions that cause uncontrolled precipitation ofthe biologically active metal into sites remote from said cationicmaterial.
 8. The method of claim 1 wherein said fibrillate fiberscomprise hydroentangled fibrillated fibers immobilized within saidintegrated paper.
 9. The method of claim 1 wherein said fibrillatefibers physical entrapment of said active agents within said integratedpaper due to said fibrillated fibers having said average fiber diameterless than said average particle size of said active agents.
 10. Themethod of claim 1 wherein said plurality of active agents are selectedfrom the group consisting of metals, metal salts, metal oxides, alumina,carbon, activated carbon, silicates, ceramics, zeolites, diatomaceousearth, activated bauxite, fuller's earth, calcium sulfate, titaniumdioxide, magnesia, magnesium hydroxide, magnesium oxide, manganeseoxides, iron oxides, perlite, talc, clay, bone char, calcium hydroxide,calcium salts, or combinations thereof.
 11. The method of claim 1wherein said fibrillated fibers and said active agents have differentsettling velocities such that said fibrillated fibers settle to onesurface of the integrated paper and the active agents settle to theother surface of the integrated paper so that an asymmetric poregradient exists through the thickness of the integrated paper.
 12. Themethod of claim 1 wherein said asymmetric pore gradient provides anintegrated paper having a pore structure from a prefiltration structureto a final polishing filter.
 13. The method of claim 1 wherein theactive agents are present in an amount of up to about 50 weight percentbased on a total weight of the integrated paper.
 14. The method of claim1 wherein the active agents are present in an amount of up to about 75weight percent based on the total weight of the integrated paper. 15.The method of claim 1 wherein the active agents are present in an amountof up to about 95 weight percent based on the total weight of theintegrated paper.
 16. The method of claim 1 further including binderfibers or particles having an average diameter equal to or less than theaverage particle size of the active agents to physically entrap theactive agents within the integrated paper.
 17. The method of claim 1wherein said integrated paper has a mean pore size of less than or equalto about 1 micron to provide supplemental direct mechanical interceptionof microbiological contaminants in combination with the microbiologicalinterception enhancing agent.
 18. The method of claim 14 wherein saidfibrillated fibers have an average diameter of less than or equal to 250nm.
 19. A method of immobilizing particles comprising the followingsteps in the sequence set forth: providing fibrillating fibers;providing a plurality of active agents wherein an average diameter ofsaid fibrillated fibers is less than an average particle size of saidactive agents; providing a cationic material on at least portions of atleast some of said fibrillated fibers and/or said active agents, saidportions having a counter ion of said cationic material; forming amicrobiological interception enhancing agent comprising a metal-cationiccomplex by treating said at least portions of at least some of saidfibrillated fibers and/or said active agents with a biologically activemetal solution to precipitate said biologically active metal with saidcounter ion of said cationic material; admixing together said treatedfibrillated fibers and said treated active agents; immobilizing saidfibrillated fibers, active agents and microbiological interceptionenhancing agent into an integrated paper.
 20. A method of immobilizingparticles comprising the following steps in the sequence set forth:providing a plurality of fibrillating fibers; providing a plurality ofactive agents wherein an average diameter of said fibrillated fibers isless than an average particle size of said active agents; providing acationic material on at least portions of at least some of saidfibrillated fibers and/or said active agents, said portions having acounter ion of said cationic material; forming a microbiologicalinterception enhancing agent comprising a metal-cationic complex bytreating said at least portions of at least some of said fibrillatedfibers and/or said active agents with a biologically active metalsolution to precipitate said biologically active metal with said counterion of said cationic material; admixing together said treatedfibrillated fibers and said treated active agents; immobilizing saidtreated admixed fibrillated fibers and active agent into an integratedpaper, whereby said fibrillated fibers hydroentangle within saidintegrated paper to physical entrap said active agents and saidmicrobiological interception enhancing agent within and throughout anentire thickness of said integrated paper.
 21. The method of claim 20wherein said metal-cationic complex is a colloidal metal precipitate ofa silver-amine-halide complex.
 22. The method of claim 20 wherein saidintegrated paper has a mean flow path of less than about 2 μm.
 23. Themethod of claim 20 wherein said microbiological interception enhancingagent is formed on both said fibrillated fibers and said active agents.24. The method of claim 20 wherein said fibrillated fibers and saidactive agents have different settling velocities such that saidfibrillated fibers settle to one surface of the integrated paper and theactive agents settle to the other surface of the integrated paper sothat an asymmetric pore gradient exists through the thickness of theintegrated paper.
 25. The method of claim 20 wherein said integratedpaper has a mean pore size of less than or equal to about 1 micron toprovide supplemental direct mechanical interception of microbiologicalcontaminants in combination with the microbiological interceptionenhancing agent.